Do I have to add each new key to every locale file by hand?

No — that's the whole point. Add a key once and StringLane writes it into every locale file at the same time, ready to fill. Rename or delete a key and the change propagates across all locales too — no pasting the same key name into five files, no find-and-replace, no key that lives in en.arb but goes silently missing from de.arb or ja.arb. Type the source string, then sweep the rest with AI or fill them in side-by-side — every locale stays in sync.

Will StringLane modify or reformat my localization files?

No — not in any of the five formats. StringLane reads your files, writes your edits back, and leaves everything else alone: ARB @key descriptions and key order, iOS .strings quoting style and comments, .xcstrings JSON shape, Android XML formatting and ordering, i18next nested-vs-flat layout and CLDR suffix convention. It saves in the same format it found. Open the same file in VS Code before and after: the diff shows only the lines you actually changed.

What happens to my files if I uninstall StringLane?

Nothing — they stay exactly where they are, valid and unmodified. StringLane writes directly to your source files the whole time, so there is no export step and no proprietary format to escape. Your Flutter project, Xcode project, or Android project has no idea StringLane ever existed. It works fine without it.

Is ARB the main format and everything else an afterthought?

All five formats — ARB (Flutter), .strings (iOS), .xcstrings (Xcode 15+ String Catalog), Android XML, and i18next JSON — are first-class. The core parser for each was built and tested independently, not shimmed on top of a JSON converter. You can open a mixed project and see missing keys flagged the same way across all of them. Plurals work per-format in their native shape: ICU for ARB and i18next, Apple variations for xcstrings, .stringsdict for iOS, and for Android.

Does StringLane conflict with FlutterIntl or gen_l10n?

No. StringLane is a file editor, not a code generator and not a build tool. It edits the .arb files that FlutterIntl and gen_l10n already consume. Your l10n.yaml, your flutter gen-l10n command, your VS Code FlutterIntl extension — all of that keeps running exactly as before. StringLane sits one layer below all of it, at the file level.

Where do my strings go when I use AI translation?

Directly to whichever of the eight providers you configure: OpenAI, Anthropic, Google Gemini, Groq, Mistral, DeepSeek, xAI, or the Local LLM provider (any OpenAI-compatible runner — Ollama, LM Studio, Jan, llama.cpp, vLLM). The cloud providers use your own API key. StringLane has no server. Your strings never pass through StringLane infrastructure because there is no StringLane infrastructure. Pick the Local LLM provider and your data never leaves your machine. All eight providers use structured-output enforcement (JSON Schema, tool calls, or response schema) so bulk translations parse reliably end-to-end.

Can I run AI translation fully offline, with no cloud?

Yes. Pick Local LLM (OpenAI-compatible) in Settings → AI, then point StringLane at a runner you already have (Ollama, LM Studio, Jan, or anything that exposes an OpenAI-compatible HTTP API). Default base URL is http://localhost:11434/v1 for Ollama; type any model name your runner has pulled. No API key needed, no network required after the model is loaded.

I already pay for too many subscriptions. Is this another one?

One-time purchase. You pay once and you own it — no annual renewal, no seat fee, no “basic tier” that locks the features you actually need behind a higher plan. Future updates within the major version are included. The current price is $49 (early-adopter). Full price after launch is $79.

I'm solo and this app might never make real money. Is this worth it?

If you have shipped or are close to shipping a localized app, yes. Adding a language goes from a weekend of file-juggling to an afternoon — add your keys once, fill every locale in one sweep — and even a single prevented release-blocking gen_l10n failure or user-facing translation gap pays for it. If localizing still feels optional right now, wait until you have four locales and a deadline. That is when this tool earns back its cost in a single afternoon.

Are there any limits on projects or keys?

No. Open as many projects as you want, with as many keys and locales as your files contain. StringLane reads directly from your file system — there's no database, no sync limit, no usage cap.

How do I find every missing translation across the project?

The Issues Panel (⌘J) lists every validation problem across the project as one row per (locale, key) — missing translations, placeholder mismatches, ICU syntax errors, length warnings, guarded-word drift. Click a row to jump to that key, hit ✨ Auto-translate per row, or sweep the whole project with Fix all with AI. The Command Palette (⌘P) also exposes "Translate all missing with AI" for one-shot fills across every locale.

How does it handle plurals in languages like Ukrainian or Polish?

When you translate a plural key into a locale that requires more forms than the source has (e.g. Ukrainian needs one, few, many, other), StringLane reads CLDR rules and auto-fills every quantity the target language needs in one click. You don't manually add + few / + many first. The visual ICU editor and per-locale plural panel handle the editing; validation badges call out quantities the target locale requires but you haven't filled.

Does StringLane work on Windows or Linux?

v1.0.0 ships macOS only — universal Apple Silicon and Intel builds, both signed and notarised by Apple. Windows and Linux builds are in active development and will follow as fast releases without breaking your stringlane.yaml project file. Drop your email at support@stringlane.app and we'll let you know the moment your platform is ready.

StringLane

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Flutter ARB · iOS .strings · .xcstrings · Android XML · i18next JSON

One place for every locale
No more file-by-file

Stop adding the same key to five files by hand. StringLane shows every locale side-by-side, fills the gaps with your own AI key, and saves straight to your source files — no cloud, no export step

IDE for localization files · Local-first · Works offline

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Sound familiar?

You already have a system. Here is why it keeps failing you.

Add one string. Now edit it five times.

A new key means opening every locale file and pasting the same key name into each one by hand — hoping you didn't typo it in de.arb or skip ja.arb entirely. The work grows with every language you support.

Comparing locales by hand is archaeology.

Open de.arb, memorize a key, switch to fr.arb, search for it, switch to ja.arb, lose your place, start over. At four locales you're not editing anymore — you're cross-referencing files in your head.

Your build passed. The translation didn't.

The key exists in every file, but the value is still in English. gen_l10n compiles clean, the tests pass, and a German user gets English UI — you find out from a 1-star review, not your toolchain.

One editor that keeps every locale in sync

Add, compare, and fill every language from a single view

en.arb

{
  "@@locale": "en",
  "appTitle": "My Flutter App",
  "@appTitle": {
    "description": "The title of the application"
  },
  "welcomeMessage": "Welcome, {name}!",
  "@welcomeMessage": {
    "description": "Greeting shown on the home screen",
    "placeholders": {
      "name": {
        "type": "String",
        "example": "Alice"
      }
    }
  },
  "itemCount": "{count, plural, one {# item} other {# items}}",
  "@itemCount": {
    "description": "Number of items in the cart",
    "placeholders": {
      "count": {
        "type": "int",
        "example": "3"
      }
    }
  },
  "lastSeen": "Last seen {when}",
  "@lastSeen": {
    "description": "Relative timestamp shown in the activity feed",
    "placeholders": {
      "when": {
        "type": "String",
        "example": "2 hours ago"
      }
    }
  },
  "settingsTitle": "Settings",
  "@settingsTitle": {
    "description": "Settings screen title"
  },
  "saveButton": "Save",
  "@saveButton": {
    "description": "Primary save action button"
  },
  "cancelButton": "Cancel",
  "@cancelButton": {
    "description": "Cancel action button"
  },
  "deleteConfirm": "Are you sure you want to delete "{label}"?",
  "@deleteConfirm": {
    "description": "Confirmation prompt before deleting an item",
    "placeholders": {
      "label": {
        "type": "String",
        "example": "My note"
      }
    }
  },
  "errorGeneric": "Something went wrong. Please try again.",
  "@errorGeneric": {
    "description": "Fallback error message"
  },
  "notificationCount": "{count, plural, zero {No} notifications} one {# notification} other {# notifications}}",
  "@notificationCount": {
    "description": "Notification badge label",
    "placeholders": {
      "count": {
        "type": "int",
        "example": "5"
      }
    }
  },
  "signOut": "Sign out",
  "@signOut": {
    "description": "Sign out button label"
  }
}

de.arb

{
  "@@locale": "de",
  "appTitle": "Meine Flutter-App",
  "@appTitle": {
    "description": "Der Titel der Anwendung"
  },
  "welcomeMessage": "Willkommen, {name}!",
  "itemCount": "{count, plural, one {# Artikel} other {# Artikel}}",
  "lastSeen": "Zuletzt gesehen {when}",
  "settingsTitle": "Einstellungen",
  "saveButton": "Speichern",
  "cancelButton": "Abbrechen",
  "deleteConfirm": "Möchten Sie "{label}" wirklich löschen?",
  "errorGeneric": "",
  "notificationCount": "{count, plural, zero {Keine Benachrichtigungen} one {# Benachrichtigung} other {# Benachrichtigungen}}",
  "signOut": "Abmelden"
}

fr.arb

{
  "@@locale": "fr",
  "appTitle": "Mon application Flutter",
  "welcomeMessage": "Bienvenue, {name} !",
  "itemCount": "{count, plural, one {# article} other {# articles}}",
  "lastSeen": "Vu pour la dernière fois {when}",
  "settingsTitle": "Paramètres",
  "saveButton": "Enregistrer",
  "cancelButton": "Annuler",
  "deleteConfirm": "Voulez-vous vraiment supprimer « {label} » ?",
  "errorGeneric": "Une erreur est survenue. Veuillez réessayer.",
  "notificationCount": "{count, plural, zero {Aucune notification} one {# notification} other {# notifications}}",
  "signOut": "Se déconnecter"
}

uk.arb

{
  "@@locale": "uk",
  "appTitle": "Мій додаток Flutter",
  "cancelButton": "Скасувати",
  "deleteConfirm": "Ви впевнені, що хочете видалити «{label}»?",
  "errorGeneric": "Щось пішло не так. Будь ласка, спробуйте ще раз.",
  "itemCount": "{count, plural, one {# елемент} other {# елементів}}",
  "lastSeen": "Останній візит {when}",
  "notificationCount": "{count, plural, zero {Немає} сповіщень} one {# сповіщення} other {# сповіщень}}",
  "saveButton": "Зберегти",
  "settingsTitle": "Налаштування",
  "signOut": "Вийти",
  "welcomeMessage": "Ласкаво просимо, {name}!"
}

ja.arb

{
  "@@locale": "ja",
  "appTitle": "マイフラッターアプリ",
  "cancelButton": "キャンセル",
  "deleteConfirm": "「{label}」を削除してもよろしいですか？",
  "errorGeneric": "問題が発生しました。もう一度お試しください。",
  "itemCount": "{count, plural, one {# 件} other {# 件}}",
  "lastSeen": "最終確認：{when}",
  "notificationCount": "{count, plural, zero {通知はありません} 通知} one {# 通知} other {# 通知}}",
  "saveButton": "保存",
  "settingsTitle": "設定",
  "signOut": "ログアウト",
  "welcomeMessage": "ようこそ、{name}さん！"
}

en.arb

{
  "@@locale": "en",
  "appTitle": "My Flutter App",
  "@appTitle": {
    "description": "The title of the application"
  },
  "welcomeMessage": "Welcome, {name}!",
  "@welcomeMessage": {
    "description": "Greeting shown on the home screen",
    "placeholders": {
      "name": {
        "type": "String",
        "example": "Alice"
      }
    }
  },
  "itemCount": "{count, plural, one {# item} other {# items}}",
  "@itemCount": {
    "description": "Number of items in the cart",
    "placeholders": {
      "count": {
        "type": "int",
        "example": "3"
      }
    }
  },
  "lastSeen": "Last seen {when}",
  "@lastSeen": {
    "description": "Relative timestamp shown in the activity feed",
    "placeholders": {
      "when": {
        "type": "String",
        "example": "2 hours ago"
      }
    }
  },
  "settingsTitle": "Settings",
  "@settingsTitle": {
    "description": "Settings screen title"
  },
  "saveButton": "Save",
  "@saveButton": {
    "description": "Primary save action button"
  },
  "cancelButton": "Cancel",
  "@cancelButton": {
    "description": "Cancel action button"
  },
  "deleteConfirm": "Are you sure you want to delete "{label}"?",
  "@deleteConfirm": {
    "description": "Confirmation prompt before deleting an item",
    "placeholders": {
      "label": {
        "type": "String",
        "example": "My note"
      }
    }
  },
  "errorGeneric": "Something went wrong. Please try again.",
  "@errorGeneric": {
    "description": "Fallback error message"
  },
  "notificationCount": "{count, plural, zero {No} notifications} one {# notification} other {# notifications}}",
  "@notificationCount": {
    "description": "Notification badge label",
    "placeholders": {
      "count": {
        "type": "int",
        "example": "5"
      }
    }
  },
  "signOut": "Sign out",
  "@signOut": {
    "description": "Sign out button label"
  }
}

de.arb

{
  "@@locale": "de",
  "appTitle": "Meine Flutter-App",
  "@appTitle": {
    "description": "Der Titel der Anwendung"
  },
  "welcomeMessage": "Willkommen, {name}!",
  "itemCount": "{count, plural, one {# Artikel} other {# Artikel}}",
  "lastSeen": "Zuletzt gesehen {when}",
  "settingsTitle": "Einstellungen",
  "saveButton": "Speichern",
  "cancelButton": "Abbrechen",
  "deleteConfirm": "Möchten Sie "{label}" wirklich löschen?",
  "errorGeneric": "",
  "notificationCount": "{count, plural, zero {Keine Benachrichtigungen} one {# Benachrichtigung} other {# Benachrichtigungen}}",
  "signOut": "Abmelden"
}

fr.arb

{
  "@@locale": "fr",
  "appTitle": "Mon application Flutter",
  "welcomeMessage": "Bienvenue, {name} !",
  "itemCount": "{count, plural, one {# article} other {# articles}}",
  "lastSeen": "Vu pour la dernière fois {when}",
  "settingsTitle": "Paramètres",
  "saveButton": "Enregistrer",
  "cancelButton": "Annuler",
  "deleteConfirm": "Voulez-vous vraiment supprimer « {label} » ?",
  "errorGeneric": "Une erreur est survenue. Veuillez réessayer.",
  "notificationCount": "{count, plural, zero {Aucune notification} one {# notification} other {# notifications}}",
  "signOut": "Se déconnecter"
}

uk.arb

{
  "@@locale": "uk",
  "appTitle": "Мій додаток Flutter",
  "cancelButton": "Скасувати",
  "deleteConfirm": "Ви впевнені, що хочете видалити «{label}»?",
  "errorGeneric": "Щось пішло не так. Будь ласка, спробуйте ще раз.",
  "itemCount": "{count, plural, one {# елемент} other {# елементів}}",
  "lastSeen": "Останній візит {when}",
  "notificationCount": "{count, plural, zero {Немає} сповіщень} one {# сповіщення} other {# сповіщень}}",
  "saveButton": "Зберегти",
  "settingsTitle": "Налаштування",
  "signOut": "Вийти",
  "welcomeMessage": "Ласкаво просимо, {name}!"
}

ja.arb

{
  "@@locale": "ja",
  "appTitle": "マイフラッターアプリ",
  "cancelButton": "キャンセル",
  "deleteConfirm": "「{label}」を削除してもよろしいですか？",
  "errorGeneric": "問題が発生しました。もう一度お試しください。",
  "itemCount": "{count, plural, one {# 件} other {# 件}}",
  "lastSeen": "最終確認：{when}",
  "notificationCount": "{count, plural, zero {通知はありません} 通知} one {# 通知} other {# 通知}}",
  "saveButton": "保存",
  "settingsTitle": "設定",
  "signOut": "ログアウト",
  "welcomeMessage": "ようこそ、{name}さん！"
}

en.arb

{
  "@@locale": "en",
  "appTitle": "My Flutter App",
  "@appTitle": {
    "description": "The title of the application"
  },
  "welcomeMessage": "Welcome, {name}!",
  "@welcomeMessage": {
    "description": "Greeting shown on the home screen",
    "placeholders": {
      "name": {
        "type": "String",
        "example": "Alice"
      }
    }
  },
  "itemCount": "{count, plural, one {# item} other {# items}}",
  "@itemCount": {
    "description": "Number of items in the cart",
    "placeholders": {
      "count": {
        "type": "int",
        "example": "3"
      }
    }
  },
  "lastSeen": "Last seen {when}",
  "@lastSeen": {
    "description": "Relative timestamp shown in the activity feed",
    "placeholders": {
      "when": {
        "type": "String",
        "example": "2 hours ago"
      }
    }
  },
  "settingsTitle": "Settings",
  "@settingsTitle": {
    "description": "Settings screen title"
  },
  "saveButton": "Save",
  "@saveButton": {
    "description": "Primary save action button"
  },
  "cancelButton": "Cancel",
  "@cancelButton": {
    "description": "Cancel action button"
  },
  "deleteConfirm": "Are you sure you want to delete "{label}"?",
  "@deleteConfirm": {
    "description": "Confirmation prompt before deleting an item",
    "placeholders": {
      "label": {
        "type": "String",
        "example": "My note"
      }
    }
  },
  "errorGeneric": "Something went wrong. Please try again.",
  "@errorGeneric": {
    "description": "Fallback error message"
  },
  "notificationCount": "{count, plural, zero {No} notifications} one {# notification} other {# notifications}}",
  "@notificationCount": {
    "description": "Notification badge label",
    "placeholders": {
      "count": {
        "type": "int",
        "example": "5"
      }
    }
  },
  "signOut": "Sign out",
  "@signOut": {
    "description": "Sign out button label"
  }
}

de.arb

{
  "@@locale": "de",
  "appTitle": "Meine Flutter-App",
  "@appTitle": {
    "description": "Der Titel der Anwendung"
  },
  "welcomeMessage": "Willkommen, {name}!",
  "itemCount": "{count, plural, one {# Artikel} other {# Artikel}}",
  "lastSeen": "Zuletzt gesehen {when}",
  "settingsTitle": "Einstellungen",
  "saveButton": "Speichern",
  "cancelButton": "Abbrechen",
  "deleteConfirm": "Möchten Sie "{label}" wirklich löschen?",
  "errorGeneric": "",
  "notificationCount": "{count, plural, zero {Keine Benachrichtigungen} one {# Benachrichtigung} other {# Benachrichtigungen}}",
  "signOut": "Abmelden"
}

fr.arb

{
  "@@locale": "fr",
  "appTitle": "Mon application Flutter",
  "welcomeMessage": "Bienvenue, {name} !",
  "itemCount": "{count, plural, one {# article} other {# articles}}",
  "lastSeen": "Vu pour la dernière fois {when}",
  "settingsTitle": "Paramètres",
  "saveButton": "Enregistrer",
  "cancelButton": "Annuler",
  "deleteConfirm": "Voulez-vous vraiment supprimer « {label} » ?",
  "errorGeneric": "Une erreur est survenue. Veuillez réessayer.",
  "notificationCount": "{count, plural, zero {Aucune notification} one {# notification} other {# notifications}}",
  "signOut": "Se déconnecter"
}

uk.arb

{
  "@@locale": "uk",
  "appTitle": "Мій додаток Flutter",
  "cancelButton": "Скасувати",
  "deleteConfirm": "Ви впевнені, що хочете видалити «{label}»?",
  "errorGeneric": "Щось пішло не так. Будь ласка, спробуйте ще раз.",
  "itemCount": "{count, plural, one {# елемент} other {# елементів}}",
  "lastSeen": "Останній візит {when}",
  "notificationCount": "{count, plural, zero {Немає} сповіщень} one {# сповіщення} other {# сповіщень}}",
  "saveButton": "Зберегти",
  "settingsTitle": "Налаштування",
  "signOut": "Вийти",
  "welcomeMessage": "Ласкаво просимо, {name}!"
}

ja.arb

{
  "@@locale": "ja",
  "appTitle": "マイフラッターアプリ",
  "cancelButton": "キャンセル",
  "deleteConfirm": "「{label}」を削除してもよろしいですか？",
  "errorGeneric": "問題が発生しました。もう一度お試しください。",
  "itemCount": "{count, plural, one {# 件} other {# 件}}",
  "lastSeen": "最終確認：{when}",
  "notificationCount": "{count, plural, zero {通知はありません} 通知} one {# 通知} other {# 通知}}",
  "saveButton": "保存",
  "settingsTitle": "設定",
  "signOut": "ログアウト",
  "welcomeMessage": "ようこそ、{name}さん！"
}

en.arb

{
  "@@locale": "en",
  "appTitle": "My Flutter App",
  "@appTitle": {
    "description": "The title of the application"
  },
  "welcomeMessage": "Welcome, {name}!",
  "@welcomeMessage": {
    "description": "Greeting shown on the home screen",
    "placeholders": {
      "name": {
        "type": "String",
        "example": "Alice"
      }
    }
  },
  "itemCount": "{count, plural, one {# item} other {# items}}",
  "@itemCount": {
    "description": "Number of items in the cart",
    "placeholders": {
      "count": {
        "type": "int",
        "example": "3"
      }
    }
  },
  "lastSeen": "Last seen {when}",
  "@lastSeen": {
    "description": "Relative timestamp shown in the activity feed",
    "placeholders": {
      "when": {
        "type": "String",
        "example": "2 hours ago"
      }
    }
  },
  "settingsTitle": "Settings",
  "@settingsTitle": {
    "description": "Settings screen title"
  },
  "saveButton": "Save",
  "@saveButton": {
    "description": "Primary save action button"
  },
  "cancelButton": "Cancel",
  "@cancelButton": {
    "description": "Cancel action button"
  },
  "deleteConfirm": "Are you sure you want to delete "{label}"?",
  "@deleteConfirm": {
    "description": "Confirmation prompt before deleting an item",
    "placeholders": {
      "label": {
        "type": "String",
        "example": "My note"
      }
    }
  },
  "errorGeneric": "Something went wrong. Please try again.",
  "@errorGeneric": {
    "description": "Fallback error message"
  },
  "notificationCount": "{count, plural, zero {No} notifications} one {# notification} other {# notifications}}",
  "@notificationCount": {
    "description": "Notification badge label",
    "placeholders": {
      "count": {
        "type": "int",
        "example": "5"
      }
    }
  },
  "signOut": "Sign out",
  "@signOut": {
    "description": "Sign out button label"
  }
}

de.arb

{
  "@@locale": "de",
  "appTitle": "Meine Flutter-App",
  "@appTitle": {
    "description": "Der Titel der Anwendung"
  },
  "welcomeMessage": "Willkommen, {name}!",
  "itemCount": "{count, plural, one {# Artikel} other {# Artikel}}",
  "lastSeen": "Zuletzt gesehen {when}",
  "settingsTitle": "Einstellungen",
  "saveButton": "Speichern",
  "cancelButton": "Abbrechen",
  "deleteConfirm": "Möchten Sie "{label}" wirklich löschen?",
  "errorGeneric": "",
  "notificationCount": "{count, plural, zero {Keine Benachrichtigungen} one {# Benachrichtigung} other {# Benachrichtigungen}}",
  "signOut": "Abmelden"
}

fr.arb

{
  "@@locale": "fr",
  "appTitle": "Mon application Flutter",
  "welcomeMessage": "Bienvenue, {name} !",
  "itemCount": "{count, plural, one {# article} other {# articles}}",
  "lastSeen": "Vu pour la dernière fois {when}",
  "settingsTitle": "Paramètres",
  "saveButton": "Enregistrer",
  "cancelButton": "Annuler",
  "deleteConfirm": "Voulez-vous vraiment supprimer « {label} » ?",
  "errorGeneric": "Une erreur est survenue. Veuillez réessayer.",
  "notificationCount": "{count, plural, zero {Aucune notification} one {# notification} other {# notifications}}",
  "signOut": "Se déconnecter"
}

uk.arb

{
  "@@locale": "uk",
  "appTitle": "Мій додаток Flutter",
  "cancelButton": "Скасувати",
  "deleteConfirm": "Ви впевнені, що хочете видалити «{label}»?",
  "errorGeneric": "Щось пішло не так. Будь ласка, спробуйте ще раз.",
  "itemCount": "{count, plural, one {# елемент} other {# елементів}}",
  "lastSeen": "Останній візит {when}",
  "notificationCount": "{count, plural, zero {Немає} сповіщень} one {# сповіщення} other {# сповіщень}}",
  "saveButton": "Зберегти",
  "settingsTitle": "Налаштування",
  "signOut": "Вийти",
  "welcomeMessage": "Ласкаво просимо, {name}!"
}

ja.arb

{
  "@@locale": "ja",
  "appTitle": "マイフラッターアプリ",
  "cancelButton": "キャンセル",
  "deleteConfirm": "「{label}」を削除してもよろしいですか？",
  "errorGeneric": "問題が発生しました。もう一度お試しください。",
  "itemCount": "{count, plural, one {# 件} other {# 件}}",
  "lastSeen": "最終確認：{when}",
  "notificationCount": "{count, plural, zero {通知はありません} 通知} one {# 通知} other {# 通知}}",
  "saveButton": "保存",
  "settingsTitle": "設定",
  "signOut": "ログアウト",
  "welcomeMessage": "ようこそ、{name}さん！"
}

Add a key once — every locale, one view

StringLane opens your folder, groups keys by namespace in the sidebar, and renders every locale for the active key side-by-side. Create a key and it lands in all of them at once, ready to fill — no pasting the same key name into five files, no toggling between editor tabs.

MALFORMED

"notificationCount" in de — unclosed brace

MISSING

"errorGeneric" exists in base but missing in de

PARAM

Placeholder mismatch in "notificationCount" for uk

Know every gap before you submit

Gaps are flagged the moment they exist — not after a build fails, not after a 1-star review. You see what's wrong before you touch the build command.

On branch main
Changes not staged for commit:
modified: lib/l10n/en.arb
modified: lib/l10n/de.arb
modified: lib/l10n/uk.arb
[main 4a2f91c] l10n: add missing translations
3 files changed, 24 insertions(+), 2 deletions(-)

Edit, save, commit — nothing else

StringLane writes directly to your ARB, .strings, XML, or JSON files on every keystroke. Your git workflow stays exactly as it is. There is no export step, no sync button, no intermediate format to manage.

Fill all missing translations — with any AI model you already use, cloud or local

Bring your own API key and bulk-translate every missing string across every locale at once. OpenAI, Anthropic, Google Gemini, Groq, Mistral, DeepSeek, xAI — or run fully offline against any OpenAI-compatible local runner (Ollama, LM Studio, Jan, llama.cpp). The Issues Panel's "Fix all with AI" sweep covers ICU errors and placeholder mismatches in the same pass. No per-character credits, no subscription layered on top.

How it works

From open folder to ship-ready in minutes

Open Your Project Folder
Point StringLane at your existing project directory. It finds every ARB, .strings, Android XML, or i18next JSON file automatically — no import dialog, no configuration file, no file picker for each locale.
See Every Locale at Once
Keys live in the sidebar, every locale for the active key fills the detail pane — Grid for short strings, List for long ones. Missing entries highlight immediately, and the Issues Panel (⌘J) lists every validation problem across the project so nothing slips through.
Add a Key — It Lands in Every Locale
Create a key once and StringLane writes it into every locale file at the same time, ready to fill. Rename or delete propagates across all locales too — no find-and-replace across five files, no key that lives in en.arb but goes silently missing from ja.arb.
Fill Gaps with AI or Type Directly
Click any empty cell and type, or sweep every missing cell across every locale via the Command Palette (⌘P) → Translate all missing. Bring your own key for OpenAI, Anthropic, Gemini, Groq, Mistral, DeepSeek, xAI — or run fully local against Ollama / LM Studio / Jan via the OpenAI-compatible Local LLM provider. No credits, no middleman.
Changes Save to Your Source Files
Every edit writes directly back to the original file on disk the moment you leave the cell. No Save button, no Export step — your git diff shows exactly what changed and nothing else.
Build and Ship, Nothing Else to Do
Close StringLane and run your build. The source file is already the right file — gen_l10n, Xcode, and the Android resource compiler find exactly what they expect.

Architecture note: StringLane runs entirely on your machine — no account, no cloud, no server your files pass through. Your locale files stay in your repo, in your exact format. A git diff before and after shows only the lines you changed.

Features

The localization IDE — built for locale files, not bolted onto a generic editor

Drop a folder. Done.
Drag your project folder onto StringLane. It detects Flutter, iOS, Android, or Web from marker files
Plurals & CLDR, done right
Edit any format's native plural shape and surface the exact forms a language needs (one/few/many for Polish, Ukrainian, Arabic). Flip string ↔ plural in one click
Metadata, generated
One click writes @key descriptions, placeholder types, and length limits for every key — the context AI and human translators need to get it right
Keyboard-first
Command Palette (⌘P), Add Key (⌘K), Issues Panel (⌘J), focus search (⌘F), Issues filter (⌘⇧I), shortcuts dialog (?)

Pricing

One price. No subscription. Yours forever.

Free Trial

$0/ 14 days

Full app, all features. No email, no account, works offline.

All five formats: ARB, .strings, .xcstrings, XML, JSON
Side-by-side locale editor
Real-time ICU & placeholder validation
AI translation — BYOK, no per-character fees
Auto-save directly to source files
14 days · no credit card · works offline

Open Your Project Folder

Early-adopter price

Full License

$49one-time

Full price after launch: $79

One-time purchase. No annual renewal. No seat fee.

Everything in Free Trial
Lifetime license — pay once, use forever
3 machine activations
All future updates within major version
Priority email support
Secured at early-adopter price ($79 after launch)

Buy Full License — $49

Instant download after purchase

Need more than 3 activations? Contact us and we'll sort it out.

FAQ

Frequently asked questions

Still have questions? Email us at support@stringlane.app

Stop juggling locale files by hand

StringLane adds a key to every locale at once and shows them side-by-side — edits saved straight to your source files, no cloud, no export step. One purchase, no subscription, yours to keep.

Start free 14-day trial

Early-adopter price: $49 one-time. Full price is $79.

One place for every localeNo more file-by-file

Sound familiar?

You already have a system. Here is why it keeps failing you.

Add one string. Now edit it five times.

Comparing locales by hand is archaeology.

Your build passed. The translation didn't.

One editor that keeps every locale in sync

Add, compare, and fill every language from a single view

Add a key once — every locale, one view

Know every gap before you submit

Edit, save, commit — nothing else

Fill all missing translations — with any AI model you already use, cloud or local

How it works

From open folder to ship-ready in minutes

Open Your Project Folder

See Every Locale at Once

Add a Key — It Lands in Every Locale

Fill Gaps with AI or Type Directly

Changes Save to Your Source Files

Build and Ship, Nothing Else to Do

Open Your Project Folder

See Every Locale at Once

Add a Key — It Lands in Every Locale

Fill Gaps with AI or Type Directly

Changes Save to Your Source Files

Build and Ship, Nothing Else to Do

Features

The localization IDE — built for locale files, not bolted onto a generic editor

Drop a folder. Done.Drag your project folder onto StringLane. It detects Flutter, iOS, Android, or Web from marker files

Plurals & CLDR, done rightEdit any format's native plural shape and surface the exact forms a language needs (one/few/many for Polish, Ukrainian, Arabic). Flip string ↔ plural in one click

Metadata, generatedOne click writes @key descriptions, placeholder types, and length limits for every key — the context AI and human translators need to get it right

Keyboard-firstCommand Palette (⌘P), Add Key (⌘K), Issues Panel (⌘J), focus search (⌘F), Issues filter (⌘⇧I), shortcuts dialog (?)

Drop a folder. Done.

Plurals & CLDR, done right

Metadata, generated

Keyboard-first

Pricing

One price. No subscription. Yours forever.

Free Trial

Full License

FAQ

Frequently asked questions

Do I have to add each new key to every locale file by hand?

Will StringLane modify or reformat my localization files?

What happens to my files if I uninstall StringLane?

Is ARB the main format and everything else an afterthought?

Does StringLane conflict with FlutterIntl or gen_l10n?

Where do my strings go when I use AI translation?

Can I run AI translation fully offline, with no cloud?

I already pay for too many subscriptions. Is this another one?

I'm solo and this app might never make real money. Is this worth it?

Are there any limits on projects or keys?

How do I find every missing translation across the project?

How does it handle plurals in languages like Ukrainian or Polish?

Does StringLane work on Windows or Linux?

Still have questions? Email us at support@stringlane.app

Stop juggling locale files by hand

One place for every locale
No more file-by-file